1. Field of the Invention
The present invention relates to a pipe joint, a metal pipe with a flange to be joined to a base member and a method for manufacturing the same, in particular, applicable to refrigerant piping or hot water piping in an air conditioner for vehicles.
2. Description of Related Art
Conventionally, a pipe joint described in JP-A-8-247357 is well known. According to the conventional pipe joint, a flange member 20 is provided with an installation bore 26, the inner diameter of which is gradually reduced from one end 20b toward the other end 20a, as shown in FIG. 7. After inserting a pipe 10 into the installation bore 26, a mandrel 80 is placed inside the pipe 10 to prevent the deformation of the inside of the pipe 10, as shown in FIG. 8. Then, the pipe 10 is pressed in an axial direction from both sides with a given clamp mechanism (not shown), as if the flange member 20 is sandwiched, as shown by an arrow 81. When the pipe 10 is pressed as mentioned above, the diameter of the pipe 10 is partly enlarged to fill a clearance B (refer to FIG. 7) between the inside surface of the installation bore 26 and the outside surface of the pipe 10, and a bulging portion 16 of the pipe 10 is formed at a position just behind an end surface 20a of the flange member 20.
As a next step, an axial pressing force is applied to the pipe 10 from the direction shown by an arrow 82 in FIG. 9 with another given clamp mechanism (not shown). Therefore, the bulging portion 16 is further crushed in an axial direction to form a final shape thereof.
Further, when an axial pressing force is applied to the pipe 10 from the direction shown by an arrow 83 in FIG. 10 with a further given clamp mechanism (not shown), the end of the pipe 10 is radially expanded. As a result, an enlarged pipe opening 17 is formed and also a groove 18 for storing an O ring 13 is formed between the enlarged pipe opening 17 and the bulging portion 16.
FIG. 11 shows an embodiment of the pipe joint manufactured as mentioned above, in which the O ring 13 is stored in the groove 18 and a periphery portion (16, 17 and 18) of the pipe 10 is inserted into an opening 32 of a joint base member 30 (joint opponent member) to connect the pipe 10 to the opening 32.
According to the conventional embodiment mentioned above, the force for joining the pipe 10 with the flange member 20 is relatively weak because the pipe 10 is not sufficiently pressed to the inside surface of the installation bore 26, as the inside of the pipe 10 is merely expanded by the pressing force toward the axial direction to the pipe 10.